1. Effect of partial Ti substitution at Zn sites on the Structural, Electronic and Magnetic Properties of Zn3P2
G. Jaiganesh and S. Mathi Jaya Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam – , Tamil Nadu, India
Author’s
RESULTS AND DISCUSSION
Magnetic semiconductors are promising materials in magneto-electronic devices as they offer the possibility of manipulating the charge and spin of the electron simultaneously [1].
Intensive research in this area has lead to the identification of several transition metal substituted magnetic semiconductors [2].
Best known diluted magnetic semiconductors with room temperature ferromagnetism belong to the III-V, II-VI and IV-VI groups [3].
The formation of magnetism in semiconductors by the introduction of nonmagnetic elements is an interesting feature in this area and it has acquired considerable interest in the recent years [4, 5].
INTRODUCTION
Two Ti atom substituted Zn3P2
One Ti atom substituted Zn3P2
C(n,r) = n! / ( r!(n - r)! )
consideration of all the possible configurations
Two ways of replacing two Zn atoms by two Ti atoms are:
the case of replacing two Zn atoms by two Ti atoms among the positions corresponding to a selected 8g symmetry
the case replacing two Zn atoms by two Ti atoms among the positions corresponding to two distinct 8g symmetries.
complex task
84 (First Way) (second way) = 324 (net ways of replacement)
considered 7 cases of replacing two Zn atoms within the positions represented by specified 8g symmetry by two Ti atoms
considered 15 cases of replacing two Zn atoms at positions represented by two distinct 8g symmetries with two Ti atoms
Zn atoms occupy 3 distinct 8g positions
A Ti atom can be substituted among any three distinct 8g positions
The second case of replacing two Ti atoms is taken at random.
II-V compounds have unusual transport and photo-voltaic properties.
Zn3P2 is an earth abundant, low cost compound, polar, mixed bond, p-type semiconducting material, easy to fabricate them as a thin-film with great potential as a photo-voltaic material [6].
There exists many works devoted to the preparation and investigation of Zn3P2 based thin-film photo-voltaic devices for solar energy application [7].
Recently, we have reported the magnetism and half-metallic property of transition metal (V, Cr, Mn, Fe, Co) substituted Zn3P2 using ab-initio techniques [8].
II-V COMPOUND SEMICONDUCTORS
Total energy calculations & Band structure Zn2.875Ti0.125P2
total energy is minimum - third distinct 8g symmetry
interatomic separation and neighbors of atoms decides the energy of a crystalline phase - substituted Ti atom is responsible for the minimum energy obtained
Ferromagnetic Phase
Heat of formation,
Calculated total energy differences (∆E) in eV, the heat of formation (∆H) in eV and net magnetic moment in µB
Compound ∆E ∆H
Net Magnetic Moment
Zn2.875Ti0.125P2
-0.208
1.22
Zn2.75Ti0.25P2
0.0
-0.211 -
Our present interest is on the investigation of the magnetism of the Zn3P2 induced by the nonmagnetic Ti elemental substitution.
the one Ti atom substituted systems prefer ferromagnetic ordering while the two Ti atoms substituted Zn3P2 shows nonmagnetic nature.
Crystal Structure of Zn3P2 compound
Primitive Tetragonal Lattice - P42/nmc (No.: 137) - 40 atoms (24 Zn and 16 P) per unit cell [9].
There exist three different type of cation atom Zn (1), Zn (2), Zn (3) and they occupy 8g sites of the space group P42/nmc whereas the anion P(1), P(2), P(3) atoms occupy the 4c, 4d and 8f sites respectively.
Total DOS of Zn2.875Ti0.125P2 and Zn2.75Ti0.25P2
Charge Density Distribution in (010) plane
Zn2.875Ti0.125P2
Zn3P2
Covalent nature
one Ti atom in Zn3P2 leads - conduction
Ti induces magnetism in Zn3P2
explores - magnetic moment – originates-3d electrons of the Ti atom.
CALCULATIONAL DETAILS
The DFT as implemented in VASP along with PAW pseudo-potential is used for the calculations [10].
cutoff energy of 525 eV and 6×6×4 (for Zn3P2) and 8×8×6 (for substituted systems) k-point mesh is used.
The optimization of the Zn3P2 and Ti substituted Zn3P2 structures were carried out.
Spin-polarized calculations are performed using the spin interpolation scheme proposed by Vosko et al [10].
“Magnetoelectronics”, edited by Mark Johnson, 1st Edition, Elsevier Academic Press, Amsterdam, 2004.
“Handbook of Spintronic Semiconductors”, edited by Weimin and Irina Buyanova, Singapore: Pan Stanford Publishing, 2010.
T. Dietl and H. Ohno, Reviews of Modern Physics, Vol. 86, (2014).
Jiji Antony et al., IEEE Trans. on magnetic, Vol. 42, No. 10, (2006).
G. Jaiganesh and S. Mathi Jaya, AIP Conf. Proc. 1665, (1-3) (2015).
Wan-Jian Yin and Yanfa Yan, J. Appl. Phys. Vol. 113, (1-5), (2013).
I. G. Stamov, N. N. Syrbu and A. V. Dorogan, Physica B, Vol. 408, (2013).
G. Jaiganesh, S. Mathi Jaya, Comp. Mat. Sci., Vol. 102, (2015).
P. Villars and L. D. Calvert, “Pearson’s hand book of Crystallographic data for Intermetallic Phases” Materials Park, OH: ASM International, Vol. 4, 4864 (1991).
REFERENCES
CONCLUSION
In this work, we have studied the influence of the partial substitution of Ti atoms at Zn sites on the electronic structure and magnetic properties of Zn3P2 using the ab-initio techniques.
We found that a single Ti atom substitution can induce magnetic property in the Zn3P2 semiconductor.
The single Ti atom substituted Zn3P2 is more stable in the ferromagnetic phase and the magnetic moment of Ti atom is μB while the net magnetic moment for the unit cell is 1.22 μB.
Magnetic stability is calculated from the total energy difference (ΔE) of the primitive cell between AFM (or FM) and NM configurations.
Acknowledgment
One of the authors (G. Jaiganesh) wishes to thank the Council of Scientific and Industrial Research, New Delhi, India for the award of Research Associateship (Grant No.: 9/532(0026)/2013 EMR-1).